The Experts below are selected from a list of 35358 Experts worldwide ranked by ideXlab platform
Kenneth S. Kendler - One of the best experts on this subject based on the ideXlab platform.
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a novel sibling based design to quantify genetic and shared environmental effects application to drug abuse alcohol use disorder and criminal behavior
Psychological Medicine, 2016Co-Authors: Kenneth S. Kendler, Paul Lichtenstein, Kristina Sundquist, Henrik Ohlsson, Alexis C Edwards, Jan SundquistAbstract:BACKGROUND: Twin Studies have been criticized for upwardly biased estimates that might contribute to the missing heritability problem.METHOD: We identified, from the general Swedish population born 1960-1990, informative sibships containing a proband, one reared-together full- or half-sibling and a full-, step- or half-sibling with varying degrees of childhood cohabitation with the proband. Estimates of genetic, shared and individual specific environment for drug abuse (DA), alcohol use disorder (AUD) and criminal behavior (CB), assessed from medical, legal or pharmacy registries, were obtained using Mplus.RESULTS: Aggregate estimates of additive genetic effects for DA, AUD and CB obtained separately in males and females varied from 0.46 to 0.73 and agreed with those obtained from monozygotic and dizygotic Twins from the same population. Of 54 heritability estimates from individual classes of informative sibling trios (3 syndromes × 9 classes of trios × 2 sexes), heritability estimates from the siblings were lower, tied and higher than those from obtained from Twins in 26, one and 27 comparisons, respectively. By contrast, of 54 shared environmental estimates, 33 were lower than those found in Twins, one tied and 20 were higher.CONCLUSIONS: With adequate information, human populations can provide many methods for estimating genetic and shared environmental effects. For the three externalizing syndromes examined, concerns that heritability estimates from Twin Studies are upwardly biased or were not generalizable to more typical kinds of siblings were not supported. Overestimation of heritability from Twin Studies is not a likely explanation for the missing heritability problem. (Less)
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the etiologic role of genetic and environmental factors in criminal behavior as determined from full and half sibling pairs an evaluation of the validity of the Twin method
Psychological Medicine, 2015Co-Authors: Kenneth S. Kendler, Sara Larsson Lonn, Hermine H Maes, Jan Sundquist, Kristina SundquistAbstract:Twin Studies have shown that criminal behavior (CB) is influenced by both genetic and shared environmental factors. Could these results be replicated using full-siblings and half-siblings?
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pathways to cannabis abuse a multi stage model from cannabis availability cannabis initiation and progression to abuse
Addiction, 2009Co-Authors: Nathan A Gillespie, Michael C Neale, Kenneth S. KendlerAbstract:Aims Although previous Twin Studies have modelled the association between drug initiation and abuse, none has included the obvious risk factor of drug availability. Our aim is to determine whether the genetic and environmental risk factors for cannabis availability also generate variation in cannabis initiation and/or progression to DSM-IV symptoms of abuse.
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schizophrenia as a complex trait evidence from a meta analysis of Twin Studies
Archives of General Psychiatry, 2003Co-Authors: Patrick F Sullivan, Kenneth S. Kendler, Michael C NealeAbstract:Context There are many published Twin Studies of schizophrenia. Although these Studies have been reviewed previously, to our knowledge, no review has provided quantitative summary estimates of the impact of genes and environment on liability to schizophrenia that also accounted for the different ascertainment strategies used. Objective To calculate meta-analytic estimates of heritability in liability and shared and individual-specific environmental effects from the pooled Twin data. Data Sources We used a structured literature search to identify all published Twin Studies of schizophrenia, including MEDLINE, dissertation, and books-in-print searches. Study Selection Of the 14 identified Studies, 12 met the minimal inclusion criteria of systematic ascertainment. Data Synthesis By using a multigroup Twin model, we found evidence for substantial additive genetic effects—the point estimate of heritability in liability to schizophrenia was 81% (95% confidence interval, 73%-90%). Notably, there was consistent evidence across these Studies for common or shared environmental influences on liability to schizophrenia—joint estimate, 11% (95% confidence interval, 3%-19%). Conclusions Despite evidence of heterogeneity across Studies, these meta-analytic results from 12 published Twin Studies of schizophrenia are consistent with a view of schizophrenia as a complex trait that results from genetic and environmental etiological influences. These results are broadly informative in that they provide no information about the specific identity of these etiological influences, but they do provide a component of a unifying empirical basis supporting the rationality of searches for underlying genetic and common environmental etiological factors.
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Twin Studies of psychiatric illness: an update.
Archives of General Psychiatry, 2001Co-Authors: Kenneth S. KendlerAbstract:This overview presents selected recent developments in Twin Studies of adult psychiatric disorders. Subjects examined include the generalizability of heritability estimates, the impact of sex on patterns of familial transmission, gene-environment interaction, Twin Studies of anxiety and eating disorders, the so-called family environment, special issues raised by Twin Studies of drug use and abuse, and gene-environment correlation. The Studies reviewed suggest that (1) the heritability of many behavioral traits may be greater in permissive than in restrictive environments and, (2) for psychiatric and drug abuse disorders, genes probably work through both traditional within-the-skin physiological pathways and outside-the-skin behavioral pathways. In the latter, genes affect aspects of the social environment, such as exposure to stressful life events and levels of social support, which in turn feed back on risk of illness. Twin Studies remain a vibrant part of the field of psychiatric genetics and an important complement to and context for current efforts to localize individual susceptibility genes.
Dorret I. Boomsma - One of the best experts on this subject based on the ideXlab platform.
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meta analysis of Twin Studies highlights the importance of genetic variation in primary school educational achievement
Trends in Neuroscience and Education, 2015Co-Authors: Eveline L De Zeeuw, Eco J C De Geus, Dorret I. BoomsmaAbstract:Abstract Children differ in their ability to learn what is taught at school. Evidence from Twin Studies suggests that genetic effects contribute to such differences. The aim of the present study was to systematically review the existing literature, including 61 Studies from 11 cohorts, on Twin Studies of educational achievement in primary school children. The meta-analysis estimated heritability, based on up to 5330 MZ and 7084 DZ Twin pairs, at 73% for reading, 49% for reading comprehension, 57% for mathematics, 44% for spelling, 64% for language and 66% for educational achievement. The importance of genetic effects on educational achievement differed between countries. Heritability was consistently high in the Netherlands across educational domains, while this was not always true for the USA and the UK. It can be concluded that genetic variation is an important contributor to the individual differences in educational achievement, with some indication for interaction with country.
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A review and meta-analysis of the heritability of specific phobia subtypes and corresponding fears
Journal of Anxiety Disorders, 2013Co-Authors: C.m.h.h. Van Houtem, Dorret I. Boomsma, Marja L. Laine, Lannie Ligthart, A.j. Van Wijk, A. De JonghAbstract:Evidence from Twin Studies suggests that genetic factors contribute to the risk of developing a fear or a phobia. The aim of the present study was to review the current literature regarding Twin Studies describing the genetic basis of specific phobias and their corresponding fears. The analysis included five Twin Studies on fears and ten Twin Studies on specific phobias. Heritability estimates of fear subtypes and specific phobia subtypes both varied widely, even within the subtypes. A meta-analysis performed on the Twin study results indicated that fears and specific phobias are moderately heritable. The highest mean heritability (±SEM) among fear subtypes was found for animal fear (45%±0.004), and among specific phobias for the blood-injury-injection phobia (33%±0.06). For most phenotypes, variance could be explained solely by additive genetic and unique environmental effects. Given the dearth of independent data on the heritability of specific phobias and fears, additional research is needed.
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genetic and environmental influences on cannabis use initiation and problematic use a meta analysis of Twin Studies
Addiction, 2010Co-Authors: Karin J H Verweij, Dorret I. Boomsma, Michael C Neale, Sarah E. Medland, Michael T Lynskey, Brendan P Zietsch, Nicholas G Martin, Jacqueline M VinkAbstract:Background Because cannabis use is associated with social, physical and psychological problems, it is important to know what causes some individuals to initiate cannabis use and a subset of those to become problematic users. Previous Twin Studies found evidence for both genetic and environmental influences on vulnerability, but due to considerable variation in the results it is difficult to draw clear conclusions regarding the relative magnitude of these influences. Methods A systematic literature search identified 28 Twin Studies on cannabis use initiation and 24 Studies on problematic cannabis use.The proportion of total variance accounted for by genes (A), shared environment (C) and unshared environment (E) in (i) initiation of cannabis use and (ii) problematic cannabis use was calculated by averaging corresponding A, C and E estimates across Studies from independent cohorts and weighting by sample size. Results For cannabis use initiation, A, C and E estimates were 48%, 25% and 27% in males and 40%, 39% and 21% in females. For problematic cannabis use A, C and E estimates were 51%, 20% and 29% for males and 59%, 15% and 26% for females. Confidence intervals of these estimates are considerably narrower than those in the source Studies. Conclusions Our results indicate that vulnerability to both cannabis use initiation and problematic use was influ- enced significantly by A, C and E.There was a trend for a greater C and lesser A component for cannabis use initiation compared to problematic use for females.
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Genetic influences on human brain structure: A review of brain imaging Studies in Twins
Human brain mapping, 2007Co-Authors: Jiska S. Peper, Dorret I. Boomsma, Rachel M. Brouwer, René S. Kahn, Hilleke E. Hulshoff PolAbstract:Twin Studies suggest that variation in human brain volume is genetically influenced. The genes involved in human brain volume variation are still largely unknown, but several candidate genes have been suggested. An overview of structural Magnetic Resonance (brain) Imaging Studies in Twins is presented, which focuses on the influence of genetic factors on variation in healthy human brain volume. Twin Studies have shown that genetic effects varied regionally within the brain, with high heritabilities of frontal lobe volumes (90-95%), moderate estimates in the hippocampus (40-69%), and environmental factors influencing several medial brain areas. High heritability estimates of brain structures were revealed for regional amounts of gray matter (density) in medial frontal cortex, Heschl's gyrus, and postcentral gyrus. In addition, moderate to high heritabilities for densities of Broca's area, anterior cingulate, hippocampus, amygdala, gray matter of the parahippocampal gyrus, and white matter of the superior occipitofrontal fasciculus were reported. The high heritability for (global) brain volumes, including the intracranium, total brain, cerebral gray, and white matter, seems to be present throughout life. Estimates of genetic and environmental influences on age-related changes in brain structure in children and adults await further longitudinal Twin-Studies. For prefrontal cortex volume, white matter, and hippocampus volumes, a number of candidate genes have been identified, whereas for other brain areas, only a few or even a single candidate gene has been found so far. New techniques such as genome-wide scans may become helpful in the search for genes that are involved in the regulation of human brain volume throughout life.
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the co morbidity of anxiety and depression in the perspective of genetic epidemiology a review of Twin and family Studies
Psychological Medicine, 2005Co-Authors: Christel M Middeldorp, Danielle C Cath, R Van Dyck, Dorret I. BoomsmaAbstract:Background. Co-morbidity within anxiety disorders, and between anxiety disorders and depression, is common. According to the theory of Gray and McNaughton, this co-morbidity is caused by recursive interconnections linking the brain regions involved in fear, anxiety and panic and by heritable personality traits such as neuroticism. In other words, co-morbidity can be explained by one disorder being an epiphenomenon of the other and by a partly shared genetic etiology. The aim of this paper is to evaluate the theory of Gray and McNaughton using the results of genetic epidemiological Studies. Method. Twenty-three Twin Studies and 12 family Studies on co-morbidity are reviewed. To compare the outcomes systematically, genetic and environmental correlations between disorders are calculated for the Twin Studies and the results from the family Studies are summarized according to the method of Klein and Riso. Results. Twin Studies show that co-morbidity within anxiety disorders and between anxiety disorders and depression is explained by a shared genetic vulnerability for both disorders. Some family Studies support this conclusion, but others suggest that co-morbidity is due to one disorder being an epiphenomenon of the other. Conclusions. Discrepancies between the Twin and family Studies seem partly due to differences in used methodology. The theory of Gray and McNaughton that neuroticism is a shared risk factor for anxiety and depression is supported. Further research should reveal the role of recursive interconnections linking brain regions. A model is proposed to simultaneously investigate the influence of neuroticism and recursive interconnections on co-morbidity.
Lindon J Eaves - One of the best experts on this subject based on the ideXlab platform.
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Parental treatment and the equal environment assumption in Twin Studies of psychiatric illness.
Psychological medicine, 1994Co-Authors: Kenneth S. Kendler, M C Neale, Andrew C Heath, Ronald C Kessler, Lindon J EavesAbstract:The validity of the Twin method depends on the equal environment assumption (EEA)--that monozygotic (MZ) and dizygotic (DZ) Twins are equally correlated in their exposure to environmental factors of aetiological importance for the trait under study. Parents may treat MZ Twins more similarly than DZ Twins thereby potentially violating the EEA. We tested this hypothesis for four common psychiatric disorders (major depression, generalized anxiety disorder, phobia, and alcoholism) in a population-based sample of female-female Twin pairs where analyses indicate sufficient statistical power meaningfully to test the EEA. Mother's and father's beliefs about their Twins' zygosity disagreed with assigned zygosity in approximately 20% of cases, often because of what they were told about their Twins' zygosity at their birth. By structural equation model-fitting, we found no evidence that mother's or father's perceived zygosity influenced Twin resemblance for any of the disorders. Compared to parents of DZ Twins, parents of MZ Twins were more likely to report that, in rearing their Twins, they emphasized their similarities more than their differences. However, by model-fitting, mothers' and fathers' approach to raising Twins had no significant influence on Twin resemblance for the four examined psychiatric disorders. These results suggest that the differential treatment of MZ and DZ Twins by their parents is unlikely to represent a significant bias in Twin Studies of these major psychiatric disorders.
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a test of the equal environment assumption in Twin Studies of psychiatric illness
Behavior Genetics, 1993Co-Authors: Kenneth S. Kendler, Michael C Neale, Andrew C Heath, Ronald C Kessler, Lindon J EavesAbstract:The traditional Twin method is predicated on the equal-environment assumption (EEA)—that monozygotic (MZ) and dizygotic (DZ) Twins are equally correlated in their exposure to environmental events of etiologic importance for the trait under study. In 1968, Scarr proposed a test of the EEA which examines the impact of phenotypic similarity in Twins of perceived versus true zygosity. We apply this test for the EEA to five common psychiatric disorders (major depression, generalized anxiety disorder, phobia, bulimia, and alcoholism), as assessed by personal interview, in 1030 female-female Twin pairs from the Virginia Twin Registry with known zygosity. We use a newly developed model-fitting approach which treats perceived zygosity as a form of specified familial environment. In 158 of the 1030 pairs (15.3%), one or both Twins disagreed with the project-assigned zygosity. Model fitting provided no evidence for a significant influence of perceived zygosity on Twin resemblance for any of the five disorders. Although limited in power, these results support the validity of the EEA in Twin Studies of psychiatric disorders.
Nancy L. Segal - One of the best experts on this subject based on the ideXlab platform.
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performing together monozygotic Twin comedians Twin research mirror image cleft lip and palate dental caries noninvasive prenatal testing capgras syndrome with folie a deux in the news athletic Twins transgendered Twins crib sharing common careers
Twin Research and Human Genetics, 2019Co-Authors: Nancy L. SegalAbstract:Twin Studies have shown that our sense of humor has an underlying genetic component, but less investigation of the origins of stand-up comedy has been undertaken. This article briefly reviews Twin research findings on humor, then describes the working partnership and social affiliation of a pair of monozygotic male Twins who perform together as stand-up comedians. The abilities, personalities and temperaments of these Twins suggest future avenues for research in this interesting area. Next, findings from Twin Studies and case reports of Twins with cleft lip and palate, dental caries, noninvasive prenatal testing and Capgras syndrome (with folie a deux) are summarized. In conclusion, recent news about athletic Twins, transgendered Twins, crib-sharing and career choice are presented.
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brazilian Twin registry a bright future for Twin Studies Twin research Twin study of alcohol consumption and mortality oxygen uptake in adolescent Twins in the news superfecundated Twins in vietnam adolescent Twin relations Twin and triplet co workers a special Twin ultrasound monozygotic Twins with different skin color identical Twin returns from space
Twin Research and Human Genetics, 2016Co-Authors: Nancy L. SegalAbstract:The establishment of the Brazilian Twin Registry for the study of genetic, social, and cultural influences on behavior is one of eleven newly funded projects in the Department of Psychology at the University of Sao Paulo. These 11 interrelated projects form the core of the university's Center for Applied Research on Well-Being and Human Behavior. An overview of the planned Twin research and activities to date is presented. Next, two recent Twin Studies are reviewed, one on the relationship between alcohol consumption and mortality, and the other on factors affecting maximal oxygen uptake. Twins cited in the media include the first identified superfecundated Twins in Vietnam, adolescent Twin relations, Twins and triplets who work together, monozygotic Twins with different skin tones and a co-Twin control study that addresses the effects of space travel.
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Twin Studies of multiple myeloma research reviews and news critique of Twin research opposite sex Twins and sexual attraction Twinning rates and assisted reproductive technology family history of multiple implantation human interest book party born t
Twin Research and Human Genetics, 2013Co-Authors: Nancy L. SegalAbstract:A foundation for studying multiple myeloma, launched by a monozygotic Twin, is described. Twin Studies of that disease are also examined. A summary of selected research Studies and news events follows, with specific reference to a new critique of Twin research, sexual attraction in separated opposite-sex Twins, Twinning rates following assisted reproductive technology and family histories of multiple implantation. Human interest topics cover a gathering of researchers from the Minnesota Study of Twins Reared Apart, morning sickness and Twin pregnancy, sexuality in conjoined Twins, a famous hidden Twin, and a film about switched at birth babies.
Michael C Neale - One of the best experts on this subject based on the ideXlab platform.
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heritability of brain ventricle volume converging evidence from inconsistent results
Neurobiology of Aging, 2012Co-Authors: William S Kremen, Matthew S Panizzon, Michael C Neale, Christine Fennemanotestine, Elizabeth Promwormley, Lisa T Eyler, Allison Stevens, Carol E Franz, Michael J Lyons, Michael D GrantAbstract:Twin Studies generally show great consistency for the heritability of brain structures. Ironically, the lateral ventricles--perhaps the most reliably measured brain regions of interest--are the most inconsistent when it comes to estimating genetic influences on their volume. Heritability estimates in Twin Studies have ranged from zero to almost 0.80. Here we aggregate heritability estimates from extant Twin Studies, and we review and reinterpret some of the findings. Based on our revised estimates, we conclude that lateral ventricular volume is indeed heritable. The weighted average heritability of the revised estimates was 0.54. Although accumulated environmental insults might seem most logical as the predominant cause of age-related ventricular expansion, the data strongly suggest that genetic influences on lateral ventricular volume are increasing with age. Genetic influences accounted for 32-35% of the variance in lateral ventricular volume in childhood, but about 75% of the variance in late middle and older age. These conclusions have implications for the basic understanding of the genetic and environmental underpinnings of normative and pathological brain aging.
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genetic and environmental influences on cannabis use initiation and problematic use a meta analysis of Twin Studies
Addiction, 2010Co-Authors: Karin J H Verweij, Dorret I. Boomsma, Michael C Neale, Sarah E. Medland, Michael T Lynskey, Brendan P Zietsch, Nicholas G Martin, Jacqueline M VinkAbstract:Background Because cannabis use is associated with social, physical and psychological problems, it is important to know what causes some individuals to initiate cannabis use and a subset of those to become problematic users. Previous Twin Studies found evidence for both genetic and environmental influences on vulnerability, but due to considerable variation in the results it is difficult to draw clear conclusions regarding the relative magnitude of these influences. Methods A systematic literature search identified 28 Twin Studies on cannabis use initiation and 24 Studies on problematic cannabis use.The proportion of total variance accounted for by genes (A), shared environment (C) and unshared environment (E) in (i) initiation of cannabis use and (ii) problematic cannabis use was calculated by averaging corresponding A, C and E estimates across Studies from independent cohorts and weighting by sample size. Results For cannabis use initiation, A, C and E estimates were 48%, 25% and 27% in males and 40%, 39% and 21% in females. For problematic cannabis use A, C and E estimates were 51%, 20% and 29% for males and 59%, 15% and 26% for females. Confidence intervals of these estimates are considerably narrower than those in the source Studies. Conclusions Our results indicate that vulnerability to both cannabis use initiation and problematic use was influ- enced significantly by A, C and E.There was a trend for a greater C and lesser A component for cannabis use initiation compared to problematic use for females.
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pathways to cannabis abuse a multi stage model from cannabis availability cannabis initiation and progression to abuse
Addiction, 2009Co-Authors: Nathan A Gillespie, Michael C Neale, Kenneth S. KendlerAbstract:Aims Although previous Twin Studies have modelled the association between drug initiation and abuse, none has included the obvious risk factor of drug availability. Our aim is to determine whether the genetic and environmental risk factors for cannabis availability also generate variation in cannabis initiation and/or progression to DSM-IV symptoms of abuse.
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schizophrenia as a complex trait evidence from a meta analysis of Twin Studies
Archives of General Psychiatry, 2003Co-Authors: Patrick F Sullivan, Kenneth S. Kendler, Michael C NealeAbstract:Context There are many published Twin Studies of schizophrenia. Although these Studies have been reviewed previously, to our knowledge, no review has provided quantitative summary estimates of the impact of genes and environment on liability to schizophrenia that also accounted for the different ascertainment strategies used. Objective To calculate meta-analytic estimates of heritability in liability and shared and individual-specific environmental effects from the pooled Twin data. Data Sources We used a structured literature search to identify all published Twin Studies of schizophrenia, including MEDLINE, dissertation, and books-in-print searches. Study Selection Of the 14 identified Studies, 12 met the minimal inclusion criteria of systematic ascertainment. Data Synthesis By using a multigroup Twin model, we found evidence for substantial additive genetic effects—the point estimate of heritability in liability to schizophrenia was 81% (95% confidence interval, 73%-90%). Notably, there was consistent evidence across these Studies for common or shared environmental influences on liability to schizophrenia—joint estimate, 11% (95% confidence interval, 3%-19%). Conclusions Despite evidence of heterogeneity across Studies, these meta-analytic results from 12 published Twin Studies of schizophrenia are consistent with a view of schizophrenia as a complex trait that results from genetic and environmental etiological influences. These results are broadly informative in that they provide no information about the specific identity of these etiological influences, but they do provide a component of a unifying empirical basis supporting the rationality of searches for underlying genetic and common environmental etiological factors.
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genetic epidemiology of major depression review and meta analysis
American Journal of Psychiatry, 2000Co-Authors: Patrick F Sullivan, Michael C Neale, Kenneth S. KendlerAbstract:OBJECTIVE: The authors conducted a meta-analysis of relevant data from primary Studies of the genetic epidemiology of major depression.METHOD: The authors searched MEDLINE and the reference lists of previous review articles to identify relevant primary Studies. On the basis of a review of family, adoption, and Twin Studies that met specific inclusion criteria, the authors derived quantitative summary statistics. RESULTS: Five family Studies met the inclusion criteria. The odds ratios for proband (subjects with major depression or comparison subjects) versus first-degree relative status (affected or unaffected with major depression) were homogeneous across the five Studies (Mantel-Haenszel odds ratio=2.84, 95% CI=2.31–3.49). No adoption study met the inclusion criteria, but the results of two of the three reports were consistent with genetic influences on liability to major depression. Five Twin Studies met the inclusion criteria, and their statistical summation suggested that familial aggregation was due ...
